In the fabrication of microelectronic components, a number of the steps involved, for instance, in preparing integrated circuit chips and the packaging for the chips (articles to which the chips are attached and protected) are etching processes. Accordingly, over the years, a number of vastly different types of etching processes to remove material, sometimes in selective areas, have been developed and are utilized in varying degrees. Moreover, the steps of etching different layers which constitute, for instance, the finished integrated circuit chip, are among the most critical and crucial steps.
One method widely employed for etching is to overlay the surface to be etched with a suitable mask and then immerse the surface and mask in a chemical solution which attacks the surface to be etched, while leaving the mask intact and while only etching other materials of the article to at most, a minimum extent.
Recently, selective etch processes employing etching compositions comprising supercritical CO2 and an organic solvent, preferably propylene carbonate, have been developed and suggested for etching various materials. Use of these compositions has provided improved properties such as a wider process window as well as enhanced selective performance.
However, use of these etching compositions results in waste streams containing the supercritical CO2, organic solvent, and a wide variety of etchant contaminants such as silicon dioxide, silicon nitride, ammonium fluoride (NH4F) and the like.
It would therefore be desirable to provide a method for treating the waste stream at least from both economic and environmental viewpoints. Moreover, proper recovery of the solvent would yield for reuse, a superior etchant as regards process control and function.